Infusion bag

ABSTRACT

An infusion bag containing a substance, for example, tea, for preparing a beverage consisting of a tube made from a rectangular strip of a thin filtering sheet material the longitudinal margins of which are folded together either with or without a covering strip so as to form a longitudinal joint consisting of at least three layers which are knurled together by a pair of meshing knurling wheels. The tube is divided by at least one transverse bend so as to form a pair of chambers for holding the infusible substance, and the opposite ends of the tube are connected to each other so as to close the bag. While one of the knurling wheels for knurling the longitudinal joint preferably has continuous teeth, the other wheel preferably has two parallel narrow rows of teeth. The tips of the teeth of at least one of the knurling wheels are preferably slightly ground off.

I United States Patent [151 3, Rambold [45] Apr. 4, 1972 54] INFUSION BAG FOREIGN PATENTS OR APPLICATIONS [72] Inventor: Adolf Rambold, Bachstrasse 8, Strump 502,755 5/1954 Canada ..99/77.l

near Dusseldorf, Germany Primary Examiner-Frank W. Lutter [22] filed: 1969 Assistant Examiner-Wil1iam L. Mentlik 2 APPLNQ; 1 339 Att0meyErnest G. Montague [57] ABSTRACT [30] Foreign Application Priority Data I An 1nfus1on bag contamlng a substance, for example, tea, for Apr. 8, 1968 Austria ..3460/68 preparing a beverage consisting of a tube made from a rectan- July 18, 1968 Austria ..6952/68 gular strip of a thin filtering sheet material the longitudinal margins of which are folded together either with or without a [52] U.S. Cl. ..99/77.1, 99/171 S, 99/ 1 71 P, covering strip so as to form a longitudinal joint consisting of at 229/48 SA least three layers which are knurled together by a pair of [51] Int. Cl .1365!) 29/02 meshing knurling Wheels The tube is divided by least one [58] Field of Search ..99/77.1, 171 s, 171 c, 171 1; transverse bend so as to form a P of chambers for holding 229 4 93 1 the infusible substance, and the opposite ends of the tube are connected to each other so as to close the bag. While one of [56] References Cited the knurling wheels for knurling the longitudinal joint preferably has continuous teeth, the other wheel preferably UNITED STATES PATENTS has two parallel narrow rows of teeth. The tips of the teeth of at least one of the knurling wheels are preferably slightly 2,146,308 2/1939 Maxfield ..99/77.1 UX ground Off. 2,574,421 11/1951 Steinberg... ....92/1.1 2,593,608 4/1952 Rambold ..99/77.1 2 Claims, 17 Drawing: Figures Patented April 4, 1972 S Sheets-Sheet 2 Patented April 4, 1972 3,653,913

S Sheets-Sheet 5 In van/0r: Q i 2 Q INFUSION BAG The present invention relates to an infusion bag containing a substance for preparing a beverage, for example, tea, which is made by interconnecting the longitudinal margins of a rectangular strip of a thin, soft, porous and preferably fibrous filtering sheet material which remains coherent also in a hot liquid, and by connecting the opposite ends of the tube which is thus formed to each other so as to close the bag.

There are infusion bags known in the art which are not produced from tubes but by applying sheets of such a material as described above upon each other and by hot-gluing the longitudinal margins of such a sheet together, and sometimes also by additionally knurling the glued margins. The knurls which are then formed usually consist of parallel rows of thin indentations of an equal length which are spaced at a small distance from each other.

Insofar as infusion bags were in the past produced from tubes, these tubes were made either by folding the longitudinal margins of a rectangular strip of the filtering sheet material together so as to form a longitudinal joint consisting of several layers of the material or by gluing, and preferably hotgluing, the longitudinal margins of the strip together which are merelyplaced upon each other, and sometimes by additionally knurling the glued margins together. The longitudinal joint as it has in the past been made for producing an infusion bag is a particular kind of what is more generally known as a longitudinal seam" in which at least one of the longitudinal margins of the strip of filtering material is enfolded by the other longitudinal margin.

When using infusion bags which are produced from a tube which is formed by connecting the longitudinal margins of a rectangular strip of a filtering material so as to form a longitudinal joint which is held together merely by folding these margins together and not by any other connecting means, it has been found that, when the bag is immersed in a liquid and especially a hot liquid, the air contained in the bag will blow up the latter and tend to escape through the longitudinal joint and will thereby partly loosen or even open the joint. If such a longitudinal joint is omitted and the margins of the filtering material are merely applied on each other and connected to each other by gluing, preferably hot-gluing, and possibly are additionally knurled together, the disadvantage occurs that the adhesive which has to be employed might affect the taste of the beverage which is prepared from the substance in the infusion bag. If the gluing operation is omitted so as to overcome this disadvantage, the longitudinal joint which is then merely formed by applying the opposite longitudinal margins of the rectangular strip loosely on each other and by connecting them only by knurling them together will come apart when the infusion bag is immersed in a liquid, for example, hot water.

It is an object of the'present invention to provide an infusion bag for preparing a beverage, for example, tea, which bag is produced without gluing from a tube which is made from a rectangular strip of a thin, soft, porous and preferably fibrous filtering sheet material which remains coherent also in a hot liquid, and by connecting the opposite longitudinal margins of this strip to each other so as to form a longitudinal joint which consists of at least three layers which are folded together and are thereafter knurled together and at least two of which consist of the margins of the strip and by connecting the opposite end portions of this tube to each other so as to close the bag which contains the infusible substance.

When speaking in connection with the present invention of a longitudinal joint consisting of at least three layers, a longitudinal seam is to be understood which is formed by enfolding at least one of the longitudinal margins of the rectangular strip either by the other longitudinal margin and/or by enfolding both longitudinal margins by means of a separate cover strip. The knurled three or more layer-joint may therefore be formed only by folding and subsequently knurling the longitudinal margins of the strip of filtering material together or by enfolding the combined longitudinal margins by a separate cover strip which is then knurled together with these margins. This cover strip may consist of the same kind of material as that of the rectangular strip or of a similarmaterial which, although it does not have to be pervious to liquids, must substantially retain its cohesive strength in a hot liquid and may be firmly combined with the longitudinal margins of the bag material itself by knurling.

In the event that the usual single row of knurls does not suffice for holding the three or more layers of the longitudinal joint firmly together, which may sometimes occur especially when the bag is made of a soft filtering sheet material, a secure joint may be attained according to the invention by providing two rows of knurls which extend parallel to, and are spaced at a small distance from each other. The deformation of the longitudinal joint by an ordinary single row of knurls when applied upon some types of filtering sheet material, especially when very soft, results in a lengthening of the longitudinal joint which does not occur on the adjacent parts of the bag and may cause the tube to become crooked or buckled or to tear adjacent to the longitudinal joint. This will be avoided according to the invention by providing the longitudinal joint with a two-row knurling since the displacement of the material which is caused by the knurling will then be distributed along and across three strips, namely to the two outer unknurled strips adjacent to the two rows of knurls and also to the central unknurled strip between these two rows. This central strip will then also take up the displaced material or may even form a small bulge. Whether or not a single row of knurls may suffice or a double row will be required depends upon the type of the filtering sheet material of which the infusion bag is made. A double row of knurls is necessary, for example, if a sheet material similar to filter paper is employed which has the following properties: weight per area 12 g/m; volumetric weight: 0.27 g/cm; thickness: 0.045 mm; composition: 60 percent of long-fibered bast fiber, 20 percent of coniferous cellulose, and 20 percent of viscose synthetic fiber; wet strength: about 300 g; degree of diffusion: above that of normal filter paper; filtering limit: a particle size of 0.01 to 0.1 mm; loose disposition of long fibers but cohesive at their points of intersection and at the outer surfaces of the material.

If a two-row knurling is provided on the longitudinal joint, it is of advantage to make each of these rows approximately one half as wide as the central unknurled part between them.

For producing the knurling on the longitudinal joint of an infusion bag according to the invention it is advisable to employ a device which comprises a pair of meshing knurling wheels which are rotatable about parallel axes and be driven in opposite directions to each other, and be pressed against each other. It is one of the features of the present invention to provide one of these knurling wheels with continuous teeth, while the teeth of the other knurling wheel are interrupted by an annular unknurled part so as to form two parallel rings of corresponding narrow teeth. Each of these two rings has preferably a width which is approximately equal to one half of the width of the central unknurled part between them which is preferably provided in the form of an annular groove.

Another feature of the invention consists in grinding off the tips of the teeth of at least one of the knurling wheels to a very small extent so as to prevent at least this wheel to exert a cutting effect during the knurling operation but to attain a stronger compressive or mashing effect. The adjacent flanks of the teeth of both knurling wheels are disposed at an angle within a range of and preferably of exactly 90, to each other.

Numerous tests have shown that a very effective knurling may be attained, for example, on a paperlike filtering material as above specified if the pitch of the teeth of the knurling wheels amounts approximately to 6 mm and the height of the teeth of a knurling wheel which are not ground off or before they are ground off amounts approximately to 0.3 mm, and if the teeth of at least one knurling wheel are ground ofi' to an extent of approximately 0.1 mm. If the angle between the flanks of each tooth amounts to 90, the face of each tooth which is ground off for a distance of 0.1 mm will then have a width of 0.2 mm. Generally speaking, as the thickness of the filtering sheet material increases, it is advisable to employ knurling wheels with teeth of a slightly larger pitch and height.

It has further been found that the limits of the pitch and size of the teeth of the knurling wheels are determined by the fact that, if these values are made too large, the knurled material will be mashed so strongly that it will tear, while at too small a pitch and size of the teeth the knurling will not be permanent.

The features and advantages of the present invention will become further apparent from the following detailed description thereof which is to be read with reference to the accompanying drawings, in which:

FIG. 1 shows a front view of an infusion bag according to the invention from which a part is cut away to show a one-row knurling on the longitudinal joint at the inner side of the bag;

FIG. 2 shows a similar view of an infusion bag with a longitudinal joint at its inner side which is provided with a tworow knurling.

FIG. 3 shows a side view of either of the bags according to FIG. 1 or FIG. 2;

FIGS. 4 to 8 show diagrammatic views of longitudinal joints of different cross-sectional shapes without a cover strip, namey.

FIG. 4 a three-layerjoint;

FIG. 5 a four-layer joint;

FIG. 6 a five-layerjoint;

FIG. 7 a seven-layer joint; and

FIG. 8 a five-layer joint differing from that according to FIG. 6;

FIGS. 9 to 12 show diagrammatic views of longitudinal joints of different cross-sectional shapes and each provided with a cover strip, namely,

FIG. 9 a six-layer joint;

FIG. 10 a four-layerjoint;

FIG. 1 1 a five-Iayerjoint; and

1 FIG. 12 a six-layer joint differing from that according to- FIG. 9;

FIGS. 13 and 14 show similar diagrammatic views of the knurling wheels and a tube for producing an infusion bag which is provided with a simple longitudinal joint without and with a cover strip, respectively;

FIG. 15 shows a perspective view of a tube with a knurled joint according to the invention in an upright position before being bent over toward one side;

FIG. 16 shows a cross section ofa part of a pair of knurling wheels in which the tips of the teeth of one of these wheels are ground off; while FIG. 17 shows a similar cross section of a part of a pair of knurling wheels in which the tips of both wheels are ground off.

The infusion bag as illustrated in the drawings is made of a tube 1 which consists of a thin, soft, porous and preferably fibrous filtering material which remains coherent in a hot liquid and is produced from a rectangular strip of this material the longitudinal margins of which are folded together either directly or together with a cover strip so as to form a longitudinal joint 2 which consists of at least three layers. A certain quantity of the infusible substance, for example, tea, is either distributed on parts of the strip or filled into the tube after the longitudinal joint 2 has been formed.

FIG. 13 illustrates a three-layer joint 2 which is shown in FIG. 4 as being bent over toward one side and applied upon the adjacent part of the tube. From this tube 1, two-chamber bags 3 or 4, as illustrated in FIG. 1 and FIG. 2, respectively, are produced each of which consists of a tube the opposite ends of which are connected to each other and are thus closed by a head fold 5, while the length of the tube is divided by a substantially central transverse fold 6 so as to form two chambers 7 and 8 each of which contains a certain quantity of the infusible substance. The head fold 5 is closed by a staple 9 which also serves for securing a string 10 to the bag. The parts of the head end of each tubular section are folded over in such a manner that the longitudinal joint 2 will be located at the inner side of the bag so that the parts of this joint of the two chambers 7 and 8 face each other.

According to the invention, the longitudinal joint 2 is knurled. While on the bag as shown in FIG. 1, the longitudinal joint 2 is provided with a single wider row 11 of knurls, the bag according to FIGS. 2 and 15 is provided with two parallel narrower rows 12 and 13 of such knurls which are separated by an unknurled central strip 14 and each of which has approximately one half of the width of this central strip 14.

As illustrated in FIGS. 4 to 12, the longitudinal joint 2 may be of different structures and be made in different manners. According to FIGS. 4 to 8, each joint 2 is formed merely of the longitudinalmargins of the material of tube 1 and is not provided with an enfolding cover strip. Not counting the wall portion of the bag upon which the joint is bent, the longitudinal joint 2 according to FIG. 4 consists of three layers. the joint according to FIG. 5 of four layers, the joint according to FIG. 6 and FIG. 8 of five layers, and the joint according to FIG. 7 of seven layers.

FIGS. 9 to 12 show each longitudinal joint 2 as being additionally provided with a cover strip 17 which according to FIG. 9 may enfold four layers, according to FIG. 10 two layers, according to FIG. 11 three layers, and according to FIG. 12 four layers of the folded material of the longitudinal margins of the bag material itself.

For carrying out the knurling operation a device is employed which is preferably installed in the infusion-bag making machine and consists of a pair of meshing knurling wheels 15 and 16 which are rotatable about parallel axes and may be pressed against each other and be driven in opposite directions to each other. If, only a single row of knurls 11 is to be applied upon the longitudinal joint as shown in FIG. 1, both knurling wheels are provided with continuous teeth as shown on the wheel 15 in FIGS. 13 and 14, which extend parallel to the axis of each wheel from one of its lateral edges to the other. If, however, a two-row knurling 12,13 is to be applied as shown in FIG. 2, one of the two knurling wheels, as shown on the wheel 16 in FIGS. 13 and 14, is provided with teeth which are centrally interrupted by an annular groove so as to form two parallel rings 16 and 16 of narrow teeth. The width of each of these rings 16 and 16" amounts approximately to one half of the width of the toothless groove 16" between these rings 16' and 16".

The tips of the teeth of one of these knurling wheels, for example, ofthe wheel 16 as shown in FIG. 16 or of both knurling wheels 15 and 16 as shown in FIG. 17 are uniformly ground off. The adjacent tooth flanks of both wheels 15 and 16 are disposed at an angle within a range of and preferably at an angle of exactly 90 relative to each other. The tips of the teeth of one or both knurling wheels are,preferably ground off for a distance of 0.1 mm so that the face of each of these teeth has a width b of 0.2 mm. The pitch t of the teeth of both wheels amounts, for example, to 0.6 mm and their full depth in the unground condition to 0.3 mm.

The limits of the tooth pitch and tooth size of both knurling wheels 15 and 16 depend upon the particular material of which each tube 1 is made and are determined by the fact that, if the pitch and the tooth size are made too large, the knurled material will be mashed too much and may therefore be torn, while at too small a pitch and tooth size the knurling will not be permanent.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to the details of such embodiments but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim is:

1. An infusion bag containing an infusible substance such as tea for preparing a beverage, and comprising a tube made substantially of a rectangular strip having opposite longitudinal margins and comprising a thin, soft filtering sheet material remaining coherent in a hot liquid,

other and for thereby closing said ends, and

said longitudinal joint being provided at least on one side thereof with two parallel rows of kmurls spaced from each other by an unknurled strip.

2. An infusion bag as defined in claim 1, in which each of said rows of knurls has a width substantially equal to one half of the width of said unknurled strip between said rows. 

2. An infusion bag as defined in claim 1, in which each of said rows of knurls has a width substantially equal to one half of the width of said unknurled strip between said rows. 